Hull for high-speed boats and the like



Get. 31, 1944. v s, MAKAROFF- I 2,361,556

HULL FOR HIGH SPEED sous AND THE LIKE Filed Jan. 20, 1943 F|G.3 24 F|G.6 29

1 110/44 SMkARoFF I 7 2 INVENTOR. Q N WWW? Patented Oct. 31, 1944 entrain :sr

HULL FOR HIGH SPEED BOATS 1 AND THE LIKE Vadim- SfilVIa'karoff, New York, NJ-Y. ApplicationJanuary 20, 1943, SerialNo. 473,029

'3'Claims. .401. 114-665) My invention relates "to hulls for high speed boats and the like and has particular reference to hulls having a step or steps at the bottom.

My invention has for its object to improve steadiness of high speed craft, particularly of variable displacement type, such as hydroplanes, seaplane hulls, glisseurs, etc.

This well known fact that on high speeds the drag or resistance due to the water skin friction absorbs a larger portion of the propulsion power of the engine, such a skin friction can be greatly reduced by introducing a transverse discontinuity of bottom lines of the hulls, technically called step.

By virtue of hydrodynamic pressure on the bottom of the hull in close vicinity of the step, the hull at sufficiently high speeds rises from the water and rides on its step, when the dynamic forces or pressure are suificient to support the total weight of the craft on relatively small area of the portion of the step, the. rest of the hull bottom being free from direct contact with the water. The resistance is thereby considerably reduced at the expense, however, of the longitudinal stability of the craft, the latter being then subjected to longitudinal oscillations. Such oscillations may be of different frequencies and amplitudes, often causing trouble and even dan- 'ger for fast going crafts equipped with transverse steps. poising.

The causes of the po-rpoising have not been fully determined. It is definitely known however, that relation of center of gravity of the craft to the longitudinal position of the step is very important. By changing the position of the step in relation to the center of gravity, the amplitude and frequency of the oscillations may be considerably reduced. Experiments have shown that for different speeds of the hull there are lower and upper limits of the angle of the trim within which there is no porpoising.

In my experiments with small models of hulls in a test tank I have found that such porpoising can be largely suppressed and even eliminated if the step is so made that its different portions are at different distances from the front end of the hull or from its center of gravity, whereby the sides receive different impulses with different periods. An artificial interference is thereby created between the right and left sides of the hull with a result that such oscillations are suppressed. Such an arrangement is especially effective for boats having two parallel hulls of a catamaran type, for seaplanes, etc., in which This phenomenon is known as porcase the two hulls are. provided with steps at different distances from the bows or centers of gravity of the hulls or floats, or staggered.

Fig. 1 is a plan View of a boat of a catamaran type embodying my invention;

Fig. 2 is an elevational view of the same;

Fig. 3 is a bottom view of a hull embodying my invention;

Fig. 4 is a bottom view of a modified hull;

Figs. 5, 6, and 7 are bottom views of other modifications of my hull.

One embodiment of my invention is shown in Figs. 1 and 2, representing a high speed boat such as a submarine spotter of a catamaran type, having two floats or hulls I and 2, connected together by braces 4, 5. A fuselage B is supported on these braces at an elevation above the floats. The propelling power is furnished by motors l with ordinary airplane propellers or airscrews 8, the motor being supported by braces 9.

The hulls are provided with steps H], H at the bottom at points intermediate of their bows and stems. The front portions of the hulls are inclined upward so that'the hulls have a tendency to rise out of water at high speeds until only the edge of the step touches'the surface I2 of the water as shown in Fig. 2. The rear portion of the hull assumes a horizontal position under such conditions so that the head-on resistance is reduced to a minimum. Air is entrained under the steps by the rapid movement of the hulls so that the space I3 is largely filled with air and broken-up particles of water which offer greatly reduced frictional resistance.

To prevent oscillations or porpoising of the boat, the steps H], H are placed at different distances from the bows of the hulls as shown in Fig. l. I have found that even a relatively small difference between these distances materially reduces the oscillations. It must be greater, of course, when the boat is designed for very high speeds and for traveling under all weather conditions.

The same effect can be obtained by providing a hull ll, with a step It placed diagonally or at an-angle to the longitudinal axis of the hull as shown in Fig. 5. Fig. '7 illustrates the application of this principle to a fiat-bottomed boat it which may have a tendency to oscillate on the edge 23 of its stern, the latter being'therefore of an angular shape as shown.

A modified boat of a catamaran type is shown in Fig. 4, the hulls or floats 2i being of an identical shape with the steps 22 at the same distances from the bows, but the floats themselves set forth in the appended claims.

being longitudinally displaced.

Other shapes of hulls are shown in Figs. 3 and 5. The step 23 of the hull 24, Fig. 3, is of a zigzag shape, asymmetric in relation to its axis, as well as step l8 of Fig. 5. Corresponding shapes for the rear edges 20 and 2'! of hulls I9, 29 are shown in Figs. 6 and 7.

Asymmetricalsteps may, :of course, cause a slight tendency for the boat to turn to the right or to the left as the case may be, but such a tendency can be easily counteracted by the cor I responding construction of the rudder. I Oscillation can be effectively suppressed, therefore, by designing the boat in such a manner that the sides of the boat will have different periods of boats and the like may be further modified without departing from the spirit of the invention, as

- of said line.

I claim as'my invention:

1. A high speed boat having two floats, the hulls of the floats having transverse steps on the outside of their bottoms, one step being forward of a line perpendicular to the longitudinal axis of the boat and the other step being aft of said line.

2. A high speed boat having two floats, the hulls of the floats having transverse steps on the outside of their bottoms, a portion of one step being forward of a line perpendicular to the longitudinal axis of the boat, and the corresponding portion of the other step being aft of the said line.

3. A high speed boat comprising hull members, the hull members having transverse steps on the outside of their bottoms, a portion of one step being forward of a line perpendicular to the longitudinal axis of the boat, and the corresponding portion of the other step being'aft VADIM S. MAKAROFF, 

